Expandable polymeric composition with improved flexibility and relative preparation process

Abstract

The present invention relates to a polymeric composition which comprises: a) vinyl aromatic polymers and/or copolymers in an amount ranging from 50% to 99% by weight, calculated with respect to the overall composition, b) a polyolefin or a relative copolymer with an ester in an amount ranging from 1% to 50% by weight, calculated with respect to the overall composition, c) olefinic elastomer grafted with a.-vinyl aromatic polymer in an amount ranging from 0.01% to 40% by weight, calculated with respect to the sum of (a)+(b), d) an expanding agent in an amount ranging from 1% to 10% by weight, calculated with respect to the sum of (a)+(b)+(c).

The invention claimed is: 
     
       1. A polymeric composition which comprises:
 a) vinyl aromatic polymers and/or copolymers in an amount ranging from 50% to 99% by weight, calculated with respect to the overall composition, 
 b) a polyolefin or a polyolefin copolymer with an ester in an amount ranging from 1% to 50% by weight, calculated with respect to the overall composition, 
 c) an olefinic elastomer grafted with a vinyl aromatic polymer in an amount ranging from 0.01% to 40% by weight, calculated with respect to the sum of (a)+(b), 
 d) an expanding agent in an amount ranging from 1% to 10% by weight, calculated with respect to the sum of (a)+(b)+(c), 
 wherein components (a) and (b) are dispersed with an average diameter ranging from 10 to 2000 nm. 
 
     
     
       2. The polymeric composition according to  claim 1 , wherein the molar ratio between the vinyl aromatic polymer and the olefinic elastomer in the grafted olefinic elastomer is higher than 0.8. 
     
     
       3. The polymeric composition according to  claim 2 , wherein the molar ratio between the vinyl aromatic polymer and the olefinic elastomer in the grafted olefinic elastomer ranges from 1 to 2. 
     
     
       4. The polymeric composition according to  claim 1 , wherein the polyolefin is present in an amount ranging from 1% to 50% by weight. 
     
     
       5. The polymeric composition according to  claim 1 , wherein the polyolefin is present in an amount ranging from 10% to 30% by weight. 
     
     
       6. The polymeric composition according to  claim 1 , wherein, in the olefinic elastomer grafted with the vinyl aromatic polymer (c), an alpha mono olefin forming it is ethylene. 
     
     
       7. The polymeric composition according to  claim 1 , wherein the grafted olefinic elastomer (c) is an elastomeric terpolymer with a Mooney viscosity, determined at 100° C., which varies within the range of 30 to 90, and an iodine number higher than 5. 
     
     
       8. The polymeric composition according to  claim 1 , wherein the vinyl aromatic polymers grafted on the olefinic elastomer have a molecular weight ranging from 50,000 to 500,000. 
     
     
       9. The polymeric composition according to  claim 1 , wherein the molecular weight of the vinyl aromatic polymer grafted on the olefinic elastomer is equal to that of the vinyl aromatic polymer of component (a). 
     
     
       10. The polymeric composition according to  claim 1 , wherein the polyolefin is an ethylene polymer having a density ranging from 0.90 to 0.97 g/cm 3 . 
     
     
       11. The polymeric composition according to  claim 1 , wherein the polyolefin is a copolymer of ethylene with a vinyl ester. 
     
     
       12. A process for preparing, in continuous mass, the polymeric composition according to  claim 1 , which comprises the following steps:
 i) if said vinyl aromatic polymer and/or copolymer (a) is in granules: 
 1. heating said vinyl aromatic polymer and/or copolymer to a temperature higher than the relative melting point together with said polyolefin or polyolefin copolymer (b) in the amount ranging from 1% to 50% by weight, and said olefinic elastomer grafted with said vinyl aromatic polymer (c) in the amount ranging from 0.01% to 40% by weight, so as to form a polymeric composition in the molten state; 
 2. subsequently incorporating said expanding agent in said polymeric composition in the molten state; 
 ii) if said vinyl aromatic polymer and/or copolymer (a) is already in the molten state, adding said polyolefin or polyolefin copolymer (b) in the amount ranging from 1% to 50% by weight, said olefinic elastomer grafted with said vinyl aromatic polymer (c) in the amount ranging from 0.01% to 40% by weight and then incorporating said expanding agent so as to form the polymeric composition. 
 
     
     
       13. A polymeric composition which comprises:
 a) vinyl aromatic polymers and/or copolymers in an amount ranging from 50% to 99% by weight, calculated with respect to the overall composition, 
 b) a copolymer of ethylene with a vinyl ester in an amount ranging from 1% to 50% by weight, calculated with respect to the overall composition, 
 c) an olefinic elastomer grafted with a vinyl aromatic polymer in an amount ranging from 0.01% to 40% by weight, calculated with respect to the sum of (a)+(b), 
 d) an expanding agent in an amount ranging from 1% to 10% by weight, calculated with respect to the sum of (a)+(b)+(c).